A great number of hull penetrators and cable couplers have evolved over the years. Most resist mechanical stresses to one degree or another and some try to maintain a watertight passageway. The wide variety of designs and the many familiar structures are too numerous to discuss at length here for all contribute in their own way to the advancement of the state of the art.
Recent advances in sophisticated signal processing technology have given designers the ability to extract meaningful data from heretofore undecipherable jumbles of signals, particularly in the higher frequency ranges. Coaxial cables have long been able to transmit such information in an increasingly satisfactory manner as they are steadily improved. Transmission and processing of minute high frequency signals requires, among other things, that there be an uninterruped, uniform continuity in the coaxial carrier. Discontinuities even in the form of sharp corners, tears, constrictions and crimps etc. in the coaxial cable's shielding create unwanted electrical reflections and other attenuation consequences caused by modification of the cable's relative geometry.
Most noticeably, conventional penetrators tend to distort a coaxial cable when the cable traverses a pressured differential, such as that found at a submerged instrumentation monitor. In addition to the compensating for a pressure differential, a designer must assure that water is blocked to keep the electronics dry. Heretofore, contemporary pressure compensation and sealing schemes compromised the transmissivity of the signals. Furthermore, conventional packing gland penetrators did not block a passageway through the cable which could lead to "hosing" along at least a portion of the cable's length.
Thus, there is a continuing need in the state of the art for a pressure-compensating, sealed penetrator which does not comprise the electrical integrity and signal transmissivity of a coaxial cable.